2011年8月13日 星期六

不信任日本政府 核監測自己來 : 下一波的災難醞釀中

Radiation in Japan

Hot concern

Japan risks another crisis over decontamination

Aug 13th 2011 | TOKYO | from the print edition

SINCE April, Kiki Tanaka and hundreds of other ordinary citizens have been uploading radiation measurements to Safecast.org, a non-profit group. On a fine summer day she drives to Nihonmatsu, 56km (35 miles) from the ruined nuclear plant at Fukushima, and notes her Geiger counter ticking higher: another step in the DIY defence against radioactivity.

This grass-roots monitoring reflects a loss of trust in the authorities. Until June the government in Tokyo took radiation measurements at just one site, as if that were enough to survey the city’s 2,200 square kilometres and 13m people. In fact levels are known to vary widely within even small areas, depending on weather patterns and building materials.

Safecast’s 20 fixed sensors and 15 mobile units, which identify “hot spots” by going from schoolyard to sandpit, seek to fill a gap in the official information. With half a million data points so far, they have tended to corroborate the government’s work, but have also revealed some places where radiation was worse than expected. “It was not until local people raised their voices that the municipal governments took it seriously,” explains Ryugo Hayano, a nuclear physicist at the University of Tokyo.

Hot spots have become a chief worry. Radiation in some parts of Fukushima city can be measured in the millisieverts per hour—a dangerous level, says an official dealing with nuclear policy. Children and pregnant women should leave, and possibly others. But the authorities are reluctant to announce bad news.

Any delay in the clean-up poses problems, as radioactive particles may seep into groundwater and contaminate crops. In a few places where the work has begun, such as Minami-Soma, people are given no guidance on handling hot material. Contaminated water drains into sewers and tainted soil sits piled under tarpaulins. Detection has been spotty. Cattle were tested, but their feed and meat were not. Even when human health is not at risk, mismanaging the clean-up does social and economic damage.

More than 10,000 people remain in shelters, five months after the tsunami that triggered the nuclear crisis. While the government dithers, Ms Tanaka and the amateur Geiger geeks at Safecast.org go where its radiation monitors do not.